Basic design of a heavy lifting vessel for the construction of prefab concrete
Report 94.3.TT.4311, Transport Engineering and Logistics.
Recent technological advancements in the fields of civil and mechanical
engineering have made it feasible to build very long bridges using
prefabricated concrete elements. Three types of elements are normally used:
caissons (substructure), pier shafts and girders. The transportation and
installation of these elements is preformed by a heavy lifting vessel.
Because the three types of elements have very dissimilar characteristic
dimensions, very specific requirements are placed on the vessel. These
requirements lead to the design and building of a vessel which is only
suited for one specific project. The vessel must be written-off during the
one project and is dismantled upon completion.
In the nearby future several more bridges are proposed to be built using
large prefab concrete elements. Therefore, in this report the possibility of
designing a more universal heavy lifting vessel capable of installing various
similar bridges is examined. This universal heavy lifting vessel will
be designed to meet a number of performance requirements which have been
extrapolated from past projects. Four different concepts are considered: A
fixed lattice gantry on a catamaran vessel, a hinged crane on each hull
of a catamaran vessel, a derrick barge and a guided elevator on a catamaran
vessel with variable width. The four concepts are evaluated according to the
criteria price, operational functionality and universality.
The results of the evaluation show that only one of the concepts (derrick
barge) is able to handle elements with varying dimensions, it is only
limited by its maximum lifting capacity and lifting height. All three other
concepts are very limited in the possible element dimensions; only elements
which are 'smaller' then the original specifications can be hoisted.
Unfortunately, the derrick barge concept has a major disadvantages which
negates the universality. The location of the hoisting points causes the
vessel to trim; thus making the operating procedure much more difficult. Of
the remaining concepts, the fixed lattice gantry is the most preferable. It
offers very quick, easy and safe operation with a minimum number of crew.
In conclusion, when preparing to design a H.L.V., the decision for either
the fixed lattice gantry or derrick barge concept will be a political
decision for the construction company. The quick operation of the fixed
gantry must be weighed against the possibly higher resale value of a derrick
barge. The prospects for a truly universal H.L.V. look bleak. The
uncertainty about the characteristics and planning of future projects makes
it unlikely that a universal H.L.V. can and will be built.
In the report also the type of hoisting gear which can be used for the lifting
of the elements is examined. This evaluation has been performed for a heavy
lifting vessel according to the fixed lattice gantry concept and for the
elements of the Prince Edward Island Bridge in Canada.
Reports on Transport Engineering and Logistics (in Dutch)
, TU Delft